In any mechanical system, moving parts are subjected to wear. Despite the fact that mechanical systems are designed and lubricated in an effort to minimize wear, wear will always exist. It is important to be able to assess engine wear and avoid unpredicted equipment failure. The presence of an excessive amount of wear metal in an engine's lubricant indicates either lubricant failure or an impending mechanical failure of the system.
Spectrometric oil analysis programs (SOAP) can serve to identify problem areas before the loss of equipment to catastrophic failure by monitoring the concentration of wear metals suspended in an engine's lubricant. The success of the SOAP system is attested to by the required routine analysis of the lubricants of all aircraft and military mechanical systems. In addition, voluntary lubricant analysis is commonplace in fleet vehicles.
At present atomic emission methods are used to detect metal ions for military samples. The advantage of this methodology is that it can detect 21 elements (Fe, Cr, Cu, Ni, Mn, Ag, Al, Mg, Pb, Si, Na, Sn, Ti, V, Cd, Ca, P, B, Mo, Zn, and Ba) in the 1-1500 ppm range simultaneously. Problems associated with this methodology are: Its inability to detect metals in particles larger than 10 microns; the expense of the equipment required; the instability of the atomic absorption spectrophotometer's flame when testing hydraulic fluids; and the inability to assign oxidation levels to any wear metals present in the oil.
There are two major components to wear in any mechanical system, mechanical wear and corrosive wear. Mechanical wear is simply the scraping of metal particles from a surface while corrosive wear is the oxidation of metal on the surface giving a species that easily crumbles from the surface often without mechanical contact. Magnesium alloys are particularly sensitive to corrosive wear. Atomic admission spectra detect fine metal particles, colloidal suspensions, and discrete ions to the same extent. Lacking the speciation between these forms of the metals precludes the assessment of wear due to corrosion and that due to mechanical abrasion.
Based on the foregoing, a need has arisen for a faster, less expensive, more accessible method of oil analysis that would be practical for both large and small fleets of vehicles.